Re: [syzbot] [bcachefs?] [squashfs?] INFO: task hung in truncate_inode_pages_final (2)

On Tue, Jul 15, 2025 at 06:09:24AM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    ec4801305969 Merge branches 'for-next/core' and 'for-next/..
> git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
> console output: https://syzkaller.appspot.com/x/log.txt?x=1323ba8c580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=9e99b6fcd403d050
> dashboard link: https://syzkaller.appspot.com/bug?extid=760777ae7038cad77437
> compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
> userspace arch: arm64
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14d38d82580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=130ba0f0580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/64d8dc107d9d/disk-ec480130.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/31280b2dee28/vmlinux-ec480130.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/b3f9fb3d09f8/Image-ec480130.gz.xz
> mounted in repro: https://storage.googleapis.com/syzbot-assets/9b3f4e51e5f9/mount_0.gz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: [email protected]
> 
> INFO: task syz-executor:6656 blocked for more than 143
> INFO: task syz-executor:6656 blocked for more than 143 seconds.
>       Not tainted 6.16.0-rc5-syzkaller-gec4801305969 #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:syz-executor    state:D stack:0     pid:6656  tgid:6656  ppid:1      task_flags:0x400140 flags:0x00000019
> Call trace:
>  __switch_to+0x414/0x834 arch/arm64/kernel/process.c:742 (T)
>  context_switch kernel/sched/core.c:5401 [inline]
>  __schedule+0x1414/0x2a28 kernel/sched/core.c:6790
>  __schedule_loop kernel/sched/core.c:6868 [inline]
>  schedule+0xb4/0x230 kernel/sched/core.c:6883
>  io_schedule+0x84/0xf0 kernel/sched/core.c:7728
>  folio_wait_bit_common+0x56c/0x9e0 mm/filemap.c:1317
>  __folio_lock mm/filemap.c:1675 [inline]
>  folio_lock include/linux/pagemap.h:1114 [inline]
>  __filemap_get_folio+0x1ec/0xc38 mm/filemap.c:1928
>  truncate_inode_pages_range+0x38c/0xe18 mm/truncate.c:388
>  truncate_inode_pages mm/truncate.c:460 [inline]
>  truncate_inode_pages_final+0x8c/0xbc mm/truncate.c:495
>  evict+0x420/0x928 fs/inode.c:812
>  dispose_list fs/inode.c:852 [inline]
>  evict_inodes+0x650/0x6e8 fs/inode.c:906
>  generic_shutdown_super+0xa0/0x2b8 fs/super.c:628
>  kill_block_super+0x44/0x90 fs/super.c:1755
>  deactivate_locked_super+0xc4/0x12c fs/super.c:474
>  deactivate_super+0xe0/0x100 fs/super.c:507
>  cleanup_mnt+0x31c/0x3ac fs/namespace.c:1417
>  __cleanup_mnt+0x20/0x30 fs/namespace.c:1424
>  task_work_run+0x1dc/0x260 kernel/task_work.c:227
>  resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
>  do_notify_resume+0x174/0x1f4 arch/arm64/kernel/entry-common.c:155
>  exit_to_user_mode_prepare arch/arm64/kernel/entry-common.c:173 [inline]
>  exit_to_user_mode arch/arm64/kernel/entry-common.c:182 [inline]
>  el0_svc+0xb8/0x180 arch/arm64/kernel/entry-common.c:880
>  el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:898
>  el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596
> 
> Showing all locks held in the system:
> 3 locks held by kworker/u8:1/14:
> 1 lock held by khungtaskd/32:
>  #0: ffff80008f8599c0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire+0x4/0x48 include/linux/rcupdate.h:330
> 2 locks held by pr/ttyAMA0/43:
> 2 locks held by getty/6289:
>  #0: ffff0000d314d0a0 (&tty->ldisc_sem){++++}-{0:0}, at: ldsem_down_read+0x3c/0x4c drivers/tty/tty_ldsem.c:340
>  #1: ffff80009ba2e2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x34c/0xfa4 drivers/tty/n_tty.c:2222
> 1 lock held by syz-executor/6656:
>  #0: ffff0000c8c7e0e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: __super_lock fs/super.c:57 [inline]
>  #0: ffff0000c8c7e0e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:72 [inline]
>  #0: ffff0000c8c7e0e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: deactivate_super+0xd8/0x100 fs/super.c:506
> 1 lock held by syz-executor/6739:
>  #0: ffff0000dbe180e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: __super_lock fs/super.c:57 [inline]
>  #0: ffff0000dbe180e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:72 [inline]
>  #0: ffff0000dbe180e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: deactivate_super+0xd8/0x100 fs/super.c:506
> 1 lock held by syz-executor/6760:
>  #0: ffff0000c90c20e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: __super_lock fs/super.c:57 [inline]
>  #0: ffff0000c90c20e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:72 [inline]
>  #0: ffff0000c90c20e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: deactivate_super+0xd8/0x100 fs/super.c:506
> 1 lock held by syz-executor/6787:
>  #0: ffff0000d3e2a0e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: __super_lock fs/super.c:57 [inline]
>  #0: ffff0000d3e2a0e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:72 [inline]
>  #0: ffff0000d3e2a0e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: deactivate_super+0xd8/0x100 fs/super.c:506
> 1 lock held by syz-executor/6808:
>  #0: ffff0000d89180e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: __super_lock fs/super.c:57 [inline]
>  #0: ffff0000d89180e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:72 [inline]
>  #0: ffff0000d89180e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: deactivate_super+0xd8/0x100 fs/super.c:506
> 1 lock held by syz-executor/6839:
>  #0: ffff0000f2aba0e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: __super_lock fs/super.c:57 [inline]
>  #0: ffff0000f2aba0e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:72 [inline]
>  #0: ffff0000f2aba0e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: deactivate_super+0xd8/0x100 fs/super.c:506
> 1 lock held by syz-executor/6876:
>  #0: ffff0000dd8f40e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: __super_lock fs/super.c:57 [inline]
>  #0: ffff0000dd8f40e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:72 [inline]
>  #0: ffff0000dd8f40e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: deactivate_super+0xd8/0x100 fs/super.c:506
> 1 lock held by syz-executor/6909:
>  #0: ffff0000eac320e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: __super_lock fs/super.c:57 [inline]
>  #0: ffff0000eac320e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:72 [inline]
>  #0: ffff0000eac320e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: deactivate_super+0xd8/0x100 fs/super.c:506
> 1 lock held by syz-executor/6942:
>  #0: ffff0000d65fa0e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: __super_lock fs/super.c:57 [inline]
>  #0: ffff0000d65fa0e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:72 [inline]
>  #0: ffff0000d65fa0e0 (&type->s_umount_key#54){+.+.}-{4:4}, at: deactivate_super+0xd8/0x100 fs/super.c:506
> 
> =============================================
> 
> 
> 
> ---
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#syz set subsystems: arm

Per the console log, bcachefs wasn't even being tested - very curious
how this got flagged as potentially bcachefs.

But, all the reports have been from the arm tree, not upstream.

I wouldn't be surprised if it's a lost wakeup, those hit arm first due
to looser memory ordering.